Piezoelectric valve system

ABSTRACT

A valve system having a valve operated by a piezoelectric device to control the flow of fluid through the valve system. Movement of the valve is controlled by a pre-stressed bender actuator that changes its shape by deforming in opposite axial directions in response to a control signal applied by an actuator control system. The valve system may comprise a common rail fuel injector, electrohydraulic actuator system, electronically-controlled fuel injector, gasoline port injector, fluid metering valve, relief valve, reducing valve, direct valve or direct-injection gasoline injector.

TECHNICAL FIELD

The present invention relates generally to valve systems for controllinga flow of fluid through a fluid passageway and, more particularly, to avalve system having a valve actuated by a piezoelectric device tocontrol the flow of fluid through the valve system.

BACKGROUND

Valve systems have been designed in the past having a valve actuated bya solenoid, piezoelectric stack or magnetorestrictive rod to control theflow of fluid through the valve system. The valve system may comprise acommon rail fuel injector, electrohydraulic actuator system,electronically-controlled fuel injector, gasoline port injector, fluidmetering valve, relief valve, reducing valve, direct valve ordirect-injection gasoline injector by way of example.

However, in solenoid-controlled valve systems, it is often difficult toaccurately control movement and positioning of the valve through thecontrol signals applied to the solenoids. This is especially true whenintermediate positioning of a solenoid-controlled valve between twoopposite, fixed positions is desired. Solenoid-controlled valves, bytheir very nature, are susceptible to variability in their operation dueto inductive delays, eddy currents, spring preloads, solenoid forcecharacteristics and varying fluid flow forces. Each of these factorsmust be considered and accounted for in a solenoid-controlled valvesystem design. Moreover, the response time of solenoids limits theminimum possible dwell times between valve actuations and makes thevalve system generally more susceptible to various sources ofvariability.

While solenoids provide large forces and have long strokes, solenoids dohave certain drawbacks. For example, first, during actuation, currentmust be continuously supplied to the solenoid in order to maintain thesolenoid in its energized position. Further, to overcome the inertia ofthe armature and provide faster response times, a solenoid is driven bya stepped current waveform. A very large current is initially providedto switch the solenoid; and after the solenoid has changed state, thedrive current is stepped down to a minimum value required to hold thesolenoid in that state. Thus, a relatively complex and high powercurrent driver is required.

In addition to requiring a relatively complex and high current powersource, the requirement of continuous current flow to maintain thesolenoid at its energized position leads to heating of the solenoid. Theexistence of such a heat source, as well as the ability to properlydissipate the heat, is often of concern depending on the environment inwhich the solenoid is used.

Additionally, the force produced by a solenoid is dependent on the airgap between the armature and stator and is not easily controlled by theinput signal. This makes the solenoid difficult to use as a proportionalactuator. Large proportional solenoids are common, but they operate nearor at the saturation point and are very inefficient. Small, relativelyfast acting non-proportional solenoids may have response times definedby the armature displacement as fast as 350 microseconds. However, thisresponse time can be a significant limitation in some applications thatrequire high repetition valve actuation rates or closely spaced events.Further, it is known that there is a substantial delay between the startof the current signal and the start of the armature motion. This is dueto the inductive delay between the voltage and magnetic flux required toexert force on the armature. In valve systems, such delays lead tovariability.

Electroactive actuators such as piezoelectric stacks andmagnetorestrictive rods eliminate the response time and proportionalityshortcomings of the solenoid. The piezoelectric stacks, due to theircapacitive behavior, offer the benefit of drawing no power during “holdin”, where actuation is maintained for a long period of time. However,these actuators have shortcomings of their own. Piezoelectric stacks andmagnetorestrictive actuators possess impressive force, but have verysmall stoke capabilities. The output of these actuators must then bemechanically or hydraulically amplified, limiting the response time andproportionality benefits that they offer. Because of their small straincapabilities, these actuators also tend to be large. Additionally, theseactuators are uni-directional, i.e., they move in only one direction inresponse to a control signal. Therefore, any valve or mass moved by theactuator requires a return biasing force, such as by a return spring, tobe applied to return the valve or mass to its original position. Often,the spring comprises a significant amount of the force required to movethe valve or mass and represents another source of variability. Also,the beneficial response time of the actuator will have no impact on thereturn of the valve or mass, as it depends completely on the returnspring.

Thus, the present invention is directed to overcoming one or more of theproblems set forth above.

SUMMARY OF THE INVENTION

While the invention is described in connection with certain embodiments,it will be understood that the invention is not limited to theseembodiments. On the contrary, the invention includes all alternatives,modifications and equivalents as may be included within the spirit andscope of the present invention.

In accordance with one embodiment of the present invention, a valvesystem, such as a common rail fuel injector by way of example, includesa valve body and a fluid chamber disposed within the valve body. Thefluid chamber is adapted to communicate with a fluid source forcontaining fluid therein. A fluid orifice communicates with the fluidchamber. A valve member mounted within the valve body is movable betweena closed position for closing the fluid orifice and an open position foropening the fluid orifice. A pre-stressed bender actuator operativelyengages the valve member and is operable to selectively move the valvemember to at least one of the closed and open positions to close andopen the fluid orifice.

In accordance with another embodiment of the present invention, a valvesystem, such as a common rail fuel injector by way of example, includesa valve body and a fluid chamber disposed within the valve body. Thefluid chamber is adapted to communicate with a fluid source forcontaining fluid therein. A fluid orifice communicates with the fluidchamber. A control fluid chamber is disposed within the valve body andis adapted to communicate with a fluid source for containing fluidtherein. The control fluid chamber is also adapted to selectivelycommunicate with a drain for draining fluid from the control fluidchamber. A valve member is mounted within the valve body and is movablebetween a closed position for closing the fluid orifice and an openposition for opening the fluid orifice. The valve member moves betweenthe open and close positions in response to a difference in fluidpressure in the fluid chamber and in the control fluid chamber. Acontrol valve member is mounted within the valve body and is operable tomove between a closed position for containing fluid within the controlfluid chamber and an open position for draining fluid from the controlfluid chamber. A pre-stressed bender actuator operatively engages thecontrol valve member and is operable to selectively move the controlvalve member to at least one of the closed and open positions.

In accordance with still yet another embodiment of the presentinvention, a valve system, such as a gasoline port injector ordirect-injection gasoline injector by way of example, includes a valvebody having a fluid inlet adapted to communicate with a fluid source anda fluid outlet adapted to emit fluid. A fluid passageway extends throughthe valve body between the fluid inlet and the fluid outlet. A valvemember is mounted at least partially in the fluid passageway and ismovable between a closed position for closing the fluid orifice and anopen position for opening the fluid orifice. A pre-stressed benderactuator operatively engages the valve member and is operable toselectively move the valve member to at least one of the closed and openpositions to close and open the fluid orifice.

In accordance with still yet another embodiment of the presentinvention, a fluid metering valve includes a fluid reservoir chamberadapted to communicate with a fluid source for containing fluid therein.A fluid outlet communicates with the fluid reservoir chamber. Apre-stressed bender actuator is operable to act directly on the fluidcontained in the fluid reservoir chamber so that a volume of fluid ismetered from the fluid outlet upon actuation of the bender actuatortoward the fluid outlet.

In accordance with still yet another embodiment of the presentinvention, a fluid metering valve includes an inlet fluid passageadapted to communicate with a fluid source for carrying fluid therein.An outlet fluid passage communicates with the inlet fluid passage. Avalve seat is disposed at a juncture of the inlet fluid passage and theoutlet fluid passage. A valve member is mounted for selective movementrelative to the valve seat between a closed position for closing fluidcommunication between the inlet fluid passage and the outlet fluidpassage and an open position for opening fluid communication between thefluid inlet passage and the fluid outlet passage to meter a volume offluid through the outlet fluid passage. A pre-stressed bender actuatoroperatively engages the valve member and is operable to selectively movethe valve member to at least one of the open and closed positions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a common railfuel injector in accordance with one embodiment of the presentinvention;

FIG. 2 is a view similar to FIG. 1 illustrating a common rail fuelinjector in accordance with a second embodiment of the presentinvention;

FIG. 3 is a view similar to FIG. 1 illustrating a common rail fuelinjector in accordance with a third embodiment of the present invention;

FIG. 4 is a view similar to FIG. 1 illustrating a common rail fuelinjector in accordance with a fourth embodiment of the presentinvention;

FIG. 5 is a view similar to FIG. 1 illustrating a common rail fuelinjector in accordance with a fifth embodiment of the present invention;

FIG. 6 is a schematic block diagram of an electrohydraulic actuatorsystem in accordance with one embodiment of the present invention;

FIGS. 7A and 7B are schematic cross-sectional views illustrating theoperation of one embodiment of an electrohydraulic actuator inaccordance with the principles of the present invention;

FIG. 8 is a schematic illustration of one embodiment of mounting apre-stressed electroactive bender actuator used in the electrohydraulicactuator of FIG. 6;

FIG. 9 is a schematic illustration of a first embodiment of apre-stressed electroactive bender actuator used in the electrohydraulicactuator of FIG. 6;

FIG. 10 is a schematic illustration of a second embodiment of apre-stressed electroactive bender actuator used in the electrohydraulicactuator of FIG. 6;

FIG. 11 is a schematic illustration of a third embodiment of apre-stressed electroactive bender actuator used in the electrohydraulicactuator of FIG. 6;

FIG. 12 is a diagrammatic view of an electronically-controlled fuelinjector system in accordance with the principles of the presentinvention;

FIGS. 13A and 13B are cross-sectional views of the fuel injector used inthe system of FIG. 12 illustrating the states of components within thefuel injector during a preinjection phase of a fuel injection cycle;

FIGS. 14A ad 14B are cross-sectional views of the fuel injector used inthe system of FIG. 12 illustrating the states of components within thefuel injector during a pilot injection phase of a fuel injection cycle;

FIGS. 15A and 15B are cross-sectional views of the fuel injector used inthe system of FIG. 12 illustrating the states of components within thefuel injector during an injection delay phase of a fuel injection cycle;

FIG. 16 is cross-sectional views of the fuel injector used in the systemof FIG. 12 illustrating the states of components within the fuelinjector during a main injection phase of a fuel injection cycle;

FIG. 17 is a schematic cross-sectional view illustrating a gasoline portinjector in accordance with one embodiment of the present invention;

FIG. 18 is a schematic cross-sectional view illustrating a gasoline portinjector in accordance with a second embodiment of the presentinvention;

FIG. 19 is a schematic illustration of one embodiment of a pre-stressedelectroactive bender actuator used in the gasoline port injector of FIG.18;

FIG. 20 is a schematic view illustrating a fluid metering valve inaccordance with one embodiment of the present invention;

FIG. 21 is a schematic view illustrating a fluid metering valve inaccordance with a second embodiment of the present invention;

FIG. 22 is a schematic view illustrating a fluid metering valve inaccordance with a third embodiment of the present invention;

FIG. 23 is a schematic view illustrating a fluid metering valve inaccordance with a fourth embodiment of the present invention;

FIG. 24 is a schematic view illustrating a relief valve or a reducingvalve in accordance with one embodiment of the present invention;

FIG. 25 is a schematic view illustrating a direct valve in accordancewith one embodiment of the present invention;

FIG. 26 is a schematic view illustrating a direct-injection gasolineinjector in accordance with one embodiment of the present invention; and

FIG. 27 is a schematic view illustrating a direct-injection gasolineinjector in accordance with a second embodiment of the presentinvention.

DETAILED DESCRIPTION

With reference to the Figures, and to FIG. 1 in particular, a commonrail fuel injector 100 a is shown in accordance with the principles ofthe present invention. Fuel injector 100 a includes a valve body 102having a high-pressure fluid rail 104 extending through the body 102that communicates with a fluid chamber 106 formed in the injector tip108. An elongated needle valve 110 is mounted to extend axially throughthe valve body 102 and includes a valve tip 112 that normally seats in avalve seat 114 to close fluid orifices 116 formed at the remote end ofthe injector tip 108. The needle valve 10 is biased to the closedposition by a biasing element, such as by a return spring 118, that actson an annular flange 120 extending radially outwardly from the needlevalve 110. The needle valve 110 is mounted for reciprocal movementwithin the valve body 102 for selectively opening and closing theorifices 116 so that fuel maybe injected into an engine combustionchamber or cylinder of a combustion engine (not shown).

In accordance with one embodiment of the present invention, as shown inFIG. 1, the needle valve 110 is connected to at least one piezoelectricdevice 122, such as a pre-stressed electroactive bender actuator, whichmay be thermally, mechanically or otherwise pre-stressed, that changesits shape by deforming in opposite axial directions in response to acontrol signal applied by an electronic control module ECM (not shown).The control signal may be a voltage signal applied by the ECM to thebender actuator 122 through a pair of electrical leads (not shown).Alternatively, the bender actuator 122 may be controlled by a currentcontrol signal as is known in the art.

The bender actuator 122 preferably has a cylindrical or diskconfiguration and includes at least one electroactive layer (not shown)positioned between a pair of electrodes (not shown), although otherconfigurations are possible as well without departing from the spiritand scope of the present invention. In a de-energized or static state,the bender actuator 122 is preferably pre-stressed to have a domedconfiguration as shown in FIG. 1. When the electrodes (not shown) of thebender actuator 122 are energized to place the bender actuator 122 in anactuated state, such as when a voltage or current control signal isapplied by the ECM (not shown), the bender actuator 122 displacesaxially by flattening out from the domed configuration. In particular,the bender actuator 122 displaces axially, i.e., flattens out, in onedirection when it is actuated in response to a control signal of onepolarity. In a de-energized state, or in response to a control signal ofan opposite polarity, the bender actuator 122 displaces axially, i.e.,returns to its domed configuration, in an opposite direction. Theapplied control signal may even cause the bender actuator 122 to dome toa greater extent beyond its static domed configuration. The benderactuator 122 is therefore bi-directional in its operation. The benderactuator 122 may be a model TH-5C actuator commercially available fromFace International, Inc. of Norfolk, Va. Other appropriate benderactuators may also be used.

Bender actuator 122 may comprise a plurality of benders actuators(configured in parallel or in series) that are individually stacked orbonded together into a single multi-layered element. While not shown,those of ordinary skill in the art will appreciate that multiple benderactuators 122 may be mounted in parallel within the valve body 102 toincrease the force applied by the bender actuators 122 to the needlevalve 110 in response to a control signal applied by the ECM (notshown). Alternatively, the bender actuators 122 may be mounted in seriesto increase the stroke of the needle valve 110 upon axial displacementof the bender actuators 122 in response to the control signal.

The bender actuator 122 is mounted within the valve body 102 by aclamping and load ring assembly, illustrated diagrammatically at 124.The structure and operation of the clamping and load ring assembly 124will be described in detail below in connection with FIGS. 7A, 7B, 8 and11. Briefly, the assembly 124 includes upper and lower clamping rings(not shown) that support the bender actuator 122 at its peripheral edgebetween the pair of clamping rings. A load ring 126 of the assembly 124is used to preloads or prestress the bender actuator 122 to apredetermined spring constant and/or axial displacement by adjusting theclamping force applied to the bender actuator 122 by the pair ofclamping rings (not shown). Increasing the clamping force on the benderactuator 122 reduces an axial displacement of the bender actuator 122 toa control signal of predetermined magnitude. Conversely, decreasing theclamping force results in a greater axial displacement of the benderactuator 122 to the control signal of predetermined magnitude.

As shown in FIG. 1, the needle valve 110 is connected to the benderactuator 122 so that the needle valve 110 will travel axially within thevalve body 102 upon axial displacement of the bender actuator 122 fromthe domed, or unactuated configuration shown in FIG. 1 to a flattened,or actuated position (not shown). In one embodiment of the presentinvention, the needle valve 110, or at least a portion thereof adjacentto the bender actuator 122, is preferably made from an electricallynonconducting material, such as zirconia for example. As will beappreciated, the needle valve 110 may be fabricated of otherelectrically insulating materials known to those skilled in the art.Alternatively, the end of the needle valve 110 adjacent the benderactuator 122 may be constructed to have an electrically nonconductiveend.

In accordance with one embodiment, connection of the needle valve 110with the bender actuator 122 is achieved by forming a hole (not shown)near the center of the bender actuator 122. An electricallynonconductive sleeve (not shown) having an electrically nonconductiveannular flange 128 is inserted through the hole (not shown) so that theflange 128 contacts a major surface 130 of the bender actuator 122. Anelectrically nonconductive washer 132 is mounted in contact with anopposite major surface 134 of the bender actuator 122. An electricallyconductive fastener 136, such as a screw, is inserted through thenonconductive sleeve (not shown) and threadably engaged with one end ofthe needle valve 110. Alternatively, an electrically nonconductivefastener 136 may be inserted directly through the hole (not shown) inthe bender actuator 122 to threadably connect with one end of the needlevalve 110. As will be appreciated, instead of using a fastener 136, theend of the needle valve 110 may be rigidly connected to the benderactuator 122 by adhesives, bonding or attaching by other means. With thebender actuator 122 rigidly connected to the needle valve 110, thebender actuator 122 is capable of moving the needle valve 110bi-directional with the bi-directional operation of the bender actuator122. While not shown, it will be appreciated that needle valve 110 maynot be rigidly connected to the bender actuator 122. Rather, one end ofthe needle valve 110 remote from the valve tip 112 engages major surface134 of the bender actuator 122 so that the needle valve 110 will travelaxially within the valve body 102 upon axial displacement of the benderactuator 122 from the domed or unactuated configuration shown in FIG. 1to a flattened, or actuated position (not shown).

In operation of the common rail fuel injector 100 a, the return spring118 biases the needle valve 110 to a closed position so that the valvetip 112 seats in the valve seat 114 to close the orifices 116. Fuel isdelivered to the fluid chamber 106 under pressure through the highpressure rail 104. During an injection cycle, the ECM (not shown)applies a control signal to the bender actuator 122 that causes thebender actuator 122 to deform or displace axially by flattening out. Asthe bender actuator 122 flattens out in response to the control signal,the needle valve 110, by virtue of its rigid connection to the benderactuator 122, lifts off of the valve seat 114 against the force ofreturn spring 118 to open the orifices 116 for an injection of fuel.After the injection cycle is complete, the control signal is eitherdiscontinued, or the polarity of the control signal is reversed, tocause the bender actuator 122 to return to its domed configuration asshown in FIG. 1. The return spring 118 assists in returning the needlevalve 110 to its closed position in contact with valve seat 114 to sealthe orifices 116.

Referring now to FIG. 2, a common rail fuel injector 100 b is shown inaccordance with an alternative second embodiment of the presentinvention, where like numerals represent like parts to the common railfuel injector 100 a of FIG. 1. In this embodiment, the return spring 118is eliminated so that the bi-directional operation of the benderactuator 122 is used to move the needle valve 110 to both its open andclosed positions. The spring rate of the bender actuator 122 may beadjusted by the clamping and load ring assembly 124 to pre-load theneedle valve 110 against the valve seat 114. Alternatively, the springrate of the bender actuator 122 may be controlled by the material and/orthickness selection of the bender actuator 122. During an injectioncycle, the bender actuator 122 is energized to move the needle valve 110to its open position as described in detail above. After the injectioncycle is complete, the polarity of the control signal is preferablyreversed to cause the bender actuator 122 to return to its domedconfiguration as shown in FIG. 2 and thereby return the needle valve 110to its closed position in contact with valve seat 114 to seal theorifices 116.

Referring now to FIG. 3, a common rail fuel injector 190 c is shown inaccordance with an alternative third embodiment of the presentinvention, where like numerals represent like parts to the common railfuel injector 100 a of FIG. 1. In this embodiment, the fuel injector 100c includes the high-pressure fluid rail 104 extending through the valvebody 102 that communicates with the fluid chamber 106 formed in theinjector tip 108. An outwardly opening, elongated check valve 138 ismounted to extend axially through the valve body 102 and includes aclosing head 140 that normally seats in a conically-shaped valve seat142 to close a fluid orifice 144 formed at the remote end of theinjector tip 108. The check valve 138 is biased to the closed positionby a biasing element, such as by a return spring 146, that acts on anannular flange 148 extending radially outwardly from the check valve138. The check valve 138 is mounted for reciprocal movement within thevalve body 102 for selectively opening and closing the orifice 144 sothat fuel may be injected into an engine combustion chamber or cylinderof a combustion engine (not shown).

In this embodiment, one end of the check valve 138 remote from theclosing head 140 engages at least one bender actuator 122. The checkvalve 138 engages the bender actuator 122 so that the check valve 138will travel axially within the valve body 102 upon axial displacement ofthe bender actuator 122 from the domed, or unactuated configurationshown in FIG. 3 to a flattened, or actuated position (not shown).

In operation of the common rail fuel injector 100 c, the return spring146 biases the outwardly opening check valve 138 to a closed position sothat the closing head 140 seats in the conically-shaped valve seat 142to close the orifice 144. Fuel is delivered to the fluid chamber 106under pressure through the high pressure rail 104. During an injectioncycle, the ECM (not shown) applies a control signal to the benderactuator 122 that causes the bender actuator 122 to deform or displaceaxially by flattening out. As the bender actuator 122 flattens out inresponse to the control signal, the check valve 138, by virtue of itsengagement with the bender actuator 122, is pushed off of theconically-shaped valve seat 142 against the force of return spring 146to open the orifice 144 for an injection of fuel. After the injectioncycle is complete, the control signal is either discontinued, or thepolarity of the control signal is reversed, to cause the bender actuator122 to return to its domed configuration as shown in FIG. 3. The returnspring 146 assists in returning the check valve 138 to its closedposition so that the closing head 140 engages the conically-shaped valveseat 142 to seal the orifice 144.

Referring now to FIG. 4, a common rail fuel injector 100 d is shown inaccordance with an alternative fourth embodiment of the presentinvention, where like numerals represent like parts to the common railfuel injector 100 c of FIG. 3. In this embodiment, the elongated checkvalve 138 is rigidly connected to the bender actuator 122 as describedin detail above in connection with FIG. 1 so that the bi-directionaloperation of the bender actuator 122 is used to move the check valve 138to both its open and closed positions. The rigid connection of the checkvalve 138 to the bender actuator 122 permits the return spring 146 to beeliminated so that the bender actuator 122 provides the necessary forceto return the check valve 138 to its closed position. As described indetail above, the spring rate of the bender actuator is adjusted by theclamping and load ring assembly 124 to pre-load the check valve 138against the conicallyshaped valve seat 142.

Referring now to FIG. 5, a common rail fuel injector 100 e is shown inaccordance with an alternative fifth embodiment of the presentinvention, where like numerals represent like parts to the common railfuel injector 100 a of FIG. 1. Fuel injector 100 e includes a valve body150 having a high-pressure fluid rail 152 extending through the body 150that communicates with a fluid chamber 154 formed in the injector tip108 and a control fluid chamber 156 formed in the valve body 150. Aneedle valve 158 is mounted to extend axially through the valve body 150and includes a valve tip 160 that normally seats in a valve seat 162 toclose fluid orifices 164 formed at the remote end of the injector tip108. The needle valve 158 is biased to the closed position by a biasingelement, such as by a return spring 166, that acts on a head 168 of theneedle valve 158. The needle valve 158 is mounted for reciprocalmovement within the valve body 150 for selectively opening and closingthe orifices 164 so that fuel may be injected into an engine combustionchamber or cylinder of a combustion engine (not shown).

The high-pressure fluid delivered to the control chamber 156 above thevalve 158 and to the fluid chamber 154 in the injector tip 108 creates aforce balance along with the return spring 166. The high pressure fluidis retained in the control chamber 156 by a control valve 170 that sealsthe control chamber 156 from a drain 171. The control valve 170 isbiased to a closed position against valve seat 172 by a biasing element,such as by a return spring 174, that acts on a closing head 176 of thecontrol valve 170. The control valve 170 is mounted for reciprocalmovement within the valve body 150 for selectively opening and closing afluid passage from the control chamber 156 to the drain 171.

Further referring to FIG. 5, one end of the control valve 170 remotefrom the closing head 176 engages at least one bender actuator 122. Thecontrol valve 170 engages the bender actuator 122 so that the controlvalve 170 will travel axially within the valve body 150 upon axialdisplacement of the bender actuator 122 from the domed, or unactuatedconfiguration shown in FIG. 5 to a flattened, or actuated position (notshown).

In operation of the common rail fuel injector 100 e, the return spring174 biases the control valve 170 to a closed position so that theclosing head 176 seats against the valve seat 172 to close the fluidpassage from the control chamber 156 to the drain 171. Fuel is deliveredunder pressure from the high pressure rail 152 to the fluid chamber 154and to the control chamber 156 to create a force balance along with thereturn spring 156.

To initiate an injection of fuel from the orifices 164, the ECM (notshown) applies a control signal to the bender actuator 122 that causesthe bender actuator 122 to deform or displace axially by flattening out.As the bender actuator 122 flattens out in response to the controlsignal, the control valve 170, by virtue of its engagement with thebender actuator 122, is pushed off of the valve seat 172 against theforce of return spring 174 to open the control chamber 56 to drain 171.This results in a pressure differential being created that lifts theneedle valve 158 off of the valve seat 162 against the force of returnspring 156 and thereby open the orifices 164 for an injection of fuel.

After the injection cycle is complete, the control signal is eitherdiscontinued, or the polarity of the control signal is reversed, tocause the bender actuator 122 to return to its domed configuration asshown in FIG. 5. The return spring 174 assists in returning the controlvalve 170 to its closed position so that the closing head 176 engagesthe valve seat 172 to seal the fluid passage from the control chamber156 to the drain 171. High pressure is restored to the control chamber156 to create a force balance along with the return spring 156 asdescribed in detail above. This results in the needle valve 158 movingto the closed position against valve seat 162 to close the orifices 164.While not shown, those of ordinary skill in the art will appreciate thatmultiple bender actuators 122 may be mounted in parallel within thevalve body 150 to increase the force applied by the bender actuators 122to the control valve 170 in response to a control signal applied by theECM (not shown). Additionally, while not shown, it will be appreciatedthat the control valve 170 could be rigidly connected to the benderactuator 122 so that the return spring 174 is eliminated. In thisembodiment, the bi-directional operation of the bender actuator 122 isused to move the control valve 170 to both its open and closed positionsand thereby control operation of the needle valve 158 as described indetail above.

With reference to FIG. 6, an electrohydraulic actuator 310 comprises ahydraulic valve 314 and an electro-mechanical actuator 312, such as apre-stressed electroactive bender actuator, which may be thermally,mechanically or otherwise pre-stressed, for example. Theelectrohydraulic actuator 310 receives pressurized hydraulic fluid froma fluid source 335, and the electrohydraulic actuator 310 is fluidlycoupled to, and controls the operation of, a device 315 such as ahydraulic valve 314 for example.

In general, to operate the device 315, an electronic control unit 328,such as an electronic control module (ECM) for example, provides acommand signal to the bender actuator 312 causing the bender actuator312 to switch from a first to a second operating state. The hydraulicvalve 314 switches from a first to a second operating state as afunction of a change in state of the bender actuator 312. The device 315switches from a first to a second operating state as a function of achange in state of the hydraulic valve 314. The bi-directionalcapability of the bender actuator 312 is used to switch or return thehydraulic valve 314 and the device 315 from their respective secondstates to their respective first states.

Referring to FIG. 7A, in accordance with the principles of the presentinvention, the bender actuator 312 comprises a pre-stressedelectroactive bender actuator, which may be thermally, mechanically orotherwise pre-stressed, that changes its shape by deforming in oppositeaxial directions in response to a control signal applied by the ECM 328.The control signal may be a voltage signal applied from the ECM 328 tothe bender actuator 312 though electrical conductors. The benderactuator 312 normally has a circular or disk configuration and includesat least one electroactive layer (not shown) positioned between a pairof electrodes (not shown), although other configurations are possible aswell without departing from the spirit and scope of the presentinvention. In an unactuated or static state, the bender actuator 312 ispreferably pre-stressed to have a domed configuration as shown in FIG.7A. When the electrodes are energized to place the bender actuator 312in an actuated state, the bender actuator 312 displaces axially to aless domed configuration as shown in FIG. 7B. The bender actuator 312may be a model TH-5C commercially available from Face International,Inc. of Norfolk, Va. Other appropriate actuators may also be used. Oneor more bender actuators 312 may comprise a plurality of benderactuators (configured in parallel or in series) that are individuallystacked or bonded together into a single multi-layered element.

The bender actuator 312 is disposed within a cavity 318 within thehousing 316 and is supported at its peripheral edge 320 between lowerand upper clamp rings 322, 324 respectively. The clamp rings arenormally made from a stiff electrically nonconductive material. Thelower clamp ring 322 is generally L-shaped in cross section and has agenerally cylindrical inner side surface 321 that locates the peripheraledge 320 of the bender actuator 312. The lower clamp ring 322 has anannular support surface 323 that supports one side of the benderactuator 312 around its peripheral edge 320. The upper clamp ring 324 isalso generally L-shaped in cross section and has a bearing surface 325that contacts an opposite side of the bender actuator 312 around itsperipheral edge 320.

A load ring 326 threadably engaged within the housing is used toprestress the bender actuator 312 with a clamping force. As the loadring 326 is tighten and loosened, the clamping force is respectivelyincreased and decreased on the peripheral edge 320 of the benderactuator 312 via the upper clamp ring 324. Increasing the clamping forceon the bender actuator 312 reduces an axial displacement of the benderactuator 312 in response to a given control signal magnitude.Conversely, decreasing the clamping force results in a greater axialdisplacement. In the embodiment of FIG. 7A, the load ring 326 applies aclamping force around the whole peripheral edge 320 of the benderactuator 312. As will be appreciated, in an alternative embodiment, thebearing surface of the upper clamp ring 324 may be notched or cut out atdifferent locations around its circumference. Thus, no clamping force isdirectly applied to the portions of the peripheral edge 320 of thebender actuator 312 that are directly opposite the cutouts in thebearing surface of the upper clamp ring 324. Alternatively, a staticload may be applied to the bender actuator 312 when the electrohydraulicactuator 310 is bolted together so that the load ring 326 is notthreadably engaged to the housing 316 according to this embodiment.

The hydraulic valve 314 is comprised of a movable valve element 330,such as, a poppet for example, disposed in a cavity 332 of a valve body334 on which the housing 316 is mounted. The hydraulic valve 314 of FIG.2A is a three-way two-position valve. As will be appreciated, othercomparably functioning valves may be used in place of the poppet 330.Hydraulic fluid is provided from a source of pressurized fluid 335 via asupply passage 336 that intersects the cavity 332. Hydraulic fluid isreturned to the fluid source 335 via drain passages 338 that alsointersects the cavity 332. Operation of the hydraulic valve 314 connectseither the supply passage 336 or the drain passage 338 to a controlpassage 340. As will be appreciated, the two-dimensional depiction ofthe passages 336, 338, 340 in FIG. 2A is schematic in nature. Often thehydraulic valve 314 is manufactured such that the passages 336, 338 and340 intersect the cavity 332 at different circumferential locations ofthe cavity 332.

In FIG. 7A, the bender actuator 312 is illustrated in its domed,unactuated, quiescent position, that is, its pre-stressed mechanicalstate; and the poppet 330 is shown in its first position. The benderactuator 312 operates in response to the ECM 328 supplying commandsignals in the form of biasing voltages of different polarities andmagnitudes. The unactuated state of the bender actuator 312 is achievedin response to the ECM 328 providing a first command signal to thebender actuator 312, such as, a DC biasing voltage of a first polarity.When in that state, a center portion 342 of the bender actuator 312 isdisplaced vertically upward to a flexed or domed position. An actuatingpin or portion 344 of the poppet 330 is mechanically biased against alower side of the center portion 342 of the bender actuator 312 by abiasing element, such as, a return spring 346 for example.

The actuating pin 344 is normally made from an electricallynonconducting material, such as, zirconia for example. As will beappreciated, the actuating pin may be fabricated of other electricallyinsulating materials known to those skilled in the art. Alternatively,the end of the actuating pin 344 that is in contact with the benderactuator 312 may be constructed to have an electrically nonconductivetip.

In the first position, the poppet 330 has a first annular sealing area348 that is separated from an annular lower seat 350 on the valve body334. Therefore, pressurized hydraulic fluid is released to flow from thesupply passage 336 to the control passage 340. When in the firstposition, the poppet 330 has a second annular sealing area 352 that isengaged with an annular upper seat 354, thereby blocking the flow ofhydraulic fluid from the control passage 340 to the drain passage 338.

When it is desired to operate or change the state of the hydraulic valve314, the ECM 328 provides a second command signal to the bender actuator312, such as, a first DC biasing voltage of a different polarity fromthe first command signal. The second command signal causes the benderactuator 312 to flex in a generally vertically downward direction to aless domed or slightly domed position. The downward motion of the benderactuator 312 overcomes the biasing force of the return spring 346 as thebender actuator 312 moves to its actuated, second position asillustrated in FIG. 7B. It should be noted that if the first commandsignal is removed, the bender actuator 312 will temporarily remain inthe position illustrated in FIG. 7B until its charge sufficiently leaksoff. Therefore, substantially less power is required to maintain thebender actuator 312 than other actuators, such as, a solenoid forexample.

Motion of the bender actuator 312 downward pushes the actuator portion342 and the poppet 330 downward to its second position. With the poppet330 at its second position, the second annular sealing area 352 isseparated from the annular upper seat 354, thereby opening the controlpassage 340 to the drain passage 338. Further, the first annular sealingarea 348 engages the annular lower seat 350 on the valve body 334, andpressurized hydraulic fluid from the supply passage 336 is blocked fromthe control passage 340.

The hydraulic valve 314 remains in the state illustrated in FIG. 7Buntil the ECM 328 provides a different or the first command signal. Whenthe ECM 328 again applies the first command signal to the benderactuator 312, the bender actuator 312 moves generally upward until itachieves the unactuated, domed first position illustrated in FIG. 7A. Itshould be noted that if the first command signal is removed, the benderactuator 312 will temporarily remain in the position illustrated in FIG.7A until its charge sufficiently leaks off. As the bender actuator 312moves upward, the return spring 346 biases the poppet 330 upward againstthe center portion 342 of the bender actuator 312. As the poppet movesupward, the second annular sealing area 352 engages against the annularupper seat 354, thereby again closing the control passage 340 from thedrain passage 338. Further, the first annular sealing area 348 separatesfrom the annular lower seat 350 on the valve body 334, therebyinitiating flow of pressurized hydraulic fluid to the control passage340.

The operation of the return spring 346 moves the poppet 330 with arelatively high force, and the poppet 330 impacts the upper valve seat354 at a relatively high velocity. Such repeated high velocity impact ofthe poppet 330 against the seat 348 causes wear and reduces the usefullives of the poppet 330 and seat 348. The bender actuator 312 is aproportional and bi-directional actuator, and those features can be usedto cushion or reduce the impact of the poppet 330 on the seat 354. Afterthe first command signal is provided to the bender actuator 312 to moveit back toward its first position as illustrated in FIG. 7A, the poppet330 is moved towards its seat by the return spring 346.

As the poppet 330 moves toward the upper seat 354, the ECM 328 appliesto the bender actuator 312 a third command signal or bias similar to,but less than, the first command signal. The third command signal causesthe bender actuator 312 to move through a small upward displacement to aslightly domed third position. That third position increases theresistance force against the operation of the return spring 346. Withthe resistance force, the velocity of the poppet 330 is reduced as isthe impact force of the poppet 330 on the seat 354. As will beappreciated, the ECM 328 can provide command signals to bender actuator312 that control both the displacement or position, velocity andacceleration of the bender actuator 312 in order to more preciselycontrol the operation of the poppet 330.

In the described embodiment with respect to FIG. 6, the clamp rings 322,324 are illustrated as generally L-shaped members in cross section inwhich the lower clamp ring 322 has a side surface 321 for locating theperipheral edge 320 of the bender actuator 312. As will be appreciated,other configurations of clamp rings may be used. For example, referringto FIG. 8, upper and lower clamp rings 360, 362 are disposed within thecavity 318 of the housing 316. The lower clamp ring 362 has an annularsupport surface 364 for supporting a lower side of the bender actuator312 about the peripheral edge 320. The upper clamp ring 360 has anannular bearing surface 366 for applying a clamping force around theperipheral edge 320 on an opposite side of the bender actuator 312. Theouter circumferential surfaces 368, 370 of the upper and lower rings360, 362 locate the rings inside the cavity 318. The load ring 326functions as previously described with respect to FIG. 6 to apply aclamping force to the peripheral edge 320 of the bender actuator 312. Aspreviously discussed, the bearing surface 366 of the upper clamp ring360 may be cut out at different locations to vary the application of theclamping force against the bender actuator 312.

The clamp rings 322, 324, 360, 362 are normally made of a stiff,electrically nonconductive material. As will be appreciated, the ringsmay be made of a conductive material if the surfaces of the benderactuator 312 contacting the rings is protected with a dielectriccoating. Alternatively, one of the above embodiments may be used witheach ring. As a further alternative, a compliant material such as rubberor a “VITON” material may be used between the clamp rings and the benderactuator in order to improve the actuator loading.

In the described embodiment, the bender actuator 312 is circular innature. Referring to FIG. 9, the bender actuator 312 a may bequadrilateral, for example, square or rectangular. Upper and lowerclamping members 372, 374, respectively, extend along sides 376 of thebender actuator 312 a that are parallel to its axis of curvature. Theclamping members 372, 374 secure the sides 376 of the bender actuator312 a in a similar manner as described with respect to FIGS. 1 and 2.Further, the clamping members 372, 374 may be of differentconfigurations similar to the clamp rings 322, 324 described earlier. Aswill be appreciated, the bender actuator 312 a may be of any shape orsize that permits it to execute the functions described herein.

Referring to FIG. 10, a bender actuator 312 b may be supported alongonly a single side 378 between upper and lower clamping members 380,382, respectively. In this embodiment, the distal end 384 of the benderactuator 312 b experiences a linear displacement in response to biasingvoltages of opposite polarities.

In the described embodiment, the electro-mechanical bender actuator 312is applied to a hydraulic valve 314 that is described as a 2-position3-way poppet valve. The concept of the present invention can be extendedto an N-position M-way poppet valve. Further, the present invention canbe used with a spool valve or any other linearly translatable valve.

In the described embodiment, the poppet 330 is held in contact with thebender actuator 312 by a return spring 346. While return springs arewidely used in combination with valves, in this application, a returnspring represents a significant force to be opposed by the benderactuator 312. Further, the variability of the spring constant of thereturn spring 346 can have a significant effect on the performance offast proportional valves. As an alternative to the use of a returnspring, referring to FIG. 11, a hole 386 is formed at the center of thebender actuator 312 c. A fastener 388, such as, a screw for example, isthreadably engaged with the end of the actuating pin 344. Thus, with thebender actuator 312 c rigidly connected to the actuating pin 344, thebender actuator 312 c is now capable of moving the actuating pin 344 andpoppet 330 bi-directional with the bi-directional operation of thebender actuator 312 c. Therefore, the need for a return spring iseliminated. As will be appreciated, instead of using a fastener 388, theend of the actuating pin 344. may be rigidly connected to the benderactuator 312 c by adhesives, bonding or attaching by other means.

With reference to the Figures, and to FIG. 12 in particular, anexemplary embodiment of an electronically-controlled fuel system 410 foremploying the present invention is shown. The exemplary fuel injectionsystem 410 is adapted for a direct-injection diesel-cycle reciprocatinginternal combustion engine. However, it should be understood that thepresent invention is also applicable to other types of engines, such asrotary engines, or modifiedcycle engines, and that the engine maycontain one or more engine combustion chambers or cylinders. The fuelsystem 410 includes a fuel injector 412, apparatus 413 for supplyingfuel to each injector 412, and apparatus 414 for electronicallycontrolling each injector 412.

The engine has at least one cylinder (not shown) wherein each cylinderintersects one or more separate injector bores (not shown), each ofwhich receives a fuel injector 412 in accordance with the principles ofthe present invention. The fuel injector 412 should pressurize a supplyof fuel from the fuel supply 413, atomize the pressurized fuel bypumping it through one or more output orifices 510, deliver the correctamount of pressurized fluid to the combustion chamber portion of thecylinder and evenly disperse the fuel throughout the combustion chamber.Each injector is comprised of an electrohydraulic injector drive 415 andan injector actuator 423. The injector drive 415 is comprised of anactuator drive 418 and an electro-mechanical actuator 419, such as apre-stressed electroactive bender actuator, which may be thermally,mechanically or otherwise pre-stressed, for example. The actuator drive418 is fluidly coupled to a source of or drain for pressurized fluid422, such as a hydraulic oil for example, and comprises a main valve 421and a hydraulic pilot valve 420 responsive to the operation of thebender actuator 419. The injector actuator 423 is comprised of apressure intensifier 416 and an injection valve system 417.

In general, to operate the injection valve system 417, the electroniccontrol 414 provides a command signal to the bender actuator 419 causingthe bender actuator 419 to move through a displacement and switch from afirst to a second operating state. The actuator drive 418 switches froma first to a second operating state as a function of a change in stateof the bender actuator 419. More specifically, as the bender actuator419 moves through its displacement, it also moves the pilot valve 420.Movement of the pilot valve 420 redirects pressurized hydraulic fluidand changes the state of the main valve 421. Further, the redirectedhydraulic fluid cause the pressure intensifier 416 and the injectionvalve system 417 to switch from first to second operating states as afunction of the change in state of the actuator drive 418, therebyeither initiating a supply of, or terminating a supply of, pressurizedfuel from the output orifice 510 of the fuel injector 412.

The fuel supplying apparatus 413 typically includes a fuel tank 424, afuel supply passage 425 fluidly coupled between the fuel tank 424 and aninlet port 429 of the fuel injector 412, a relatively low pressure fueltransfer pump 426, one or more fuel filters 427, and a fuel drainpassage 428 fluidly coupled between the injector 412 and the fuel tank424. If desired, fuel passages may be disposed in the head of the enginethat are fluidly coupled with the fuel injector 412 and one or both ofthe passages 425, 428.

The electronic control apparatus 414 preferably includes an electroniccontrol module (ECM) 430 which controls at least: (1) fuel injectiontiming and pressure; (2) total fuel injection quantity during aninjection cycle; (3) the phases during each segment of each injectioncycle; (4) the number of separate injection segments during eachinjection cycle; (5) the time interval(s) between the injectionsegments; and (6) the fuel quantity delivered during each injectionsegment of each injection cycle.

Normally, each injector 412 is a unit injector wherein the injectordrive 415, pressure intensifier 416 and injection valve system 417 aredisposed in a common housing 432. Although shown as a unitized injector412, the injector 412 could alternatively be of a modular constructionwherein the pressure intensifier 416 is separate from the injectionvalve system 417. As a further alternative, the injector drive 415 maybe separated from the pressure intensifier 416.

Referring to FIG. 13A, in accordance with the principles of the presentinvention, the bender actuator 419 comprises a pre-stressedelectroactive bender actuator, which may be thermally, mechanically orotherwise pre-stressed, that changes its shape by deforming in oppositeaxial directions in response to a control signal applied by the ECM 430.The control signal may be a voltage signal applied from the ECM 430 tothe bender actuator 419 through a pair of electrical conductors 434. Thebender actuator 419 normally has a circular or disk configuration andincludes at least one electroactive layer (not shown) positioned betweena pair of electrodes (not shown), although other configurations arepossible as well without departing from the spirit and scope of thepresent invention. In an unactuated or static state, the bender actuator419 is preferably pre-stressed to have a domed configuration as shown inFIG. 13A. When the electrodes are energized to place the bender actuator419 in an actuated state, the bender actuator 419 displaces axially to aless domed configuration as shown in FIG. 13B.

The bender actuator 419 may be a model TH-5C commercially available fromFace International, Inc. of Norfolk, Va. Other appropriate actuators mayalso be used. One or more bender actuators 419 may comprise a pluralityof bender actuators (configured in parallel or in series) that areindividually stacked or bonded together into a single multi-layeredelement.

Referring to FIGS. 13A and 13B, the bender actuator 419 is disposedwithin the housing 432 and is supported at its peripheral edge 436between lower and upper clamp rings 438, 440, respectively. The clamprings are normally made from a stiff electrically nonconductivematerial. The lower clamp ring 438 is generally L-shaped in crosssection and has an annular support surface for supporting a lower sideof the bender actuator 419 around its peripheral edge 436. The upperclamp ring 440 is also generally L-shaped in cross section and has abearing surface that contacts an upper side of the bender actuator 419around its peripheral edge 436. As will be appreciated, otherconfigurations of the clamp rings 438, 440 may be used.

A load ring 442, threadably engaged within the housing 432, is used toprestress the bender actuator 419 with a clamping force. As the loadring 442 is tighten and loosened, the clamping force is respectivelyincreased and decreased on the peripheral edge 436 of the benderactuator 419 via the upper clamp ring 440. Increasing the clamping forceon the bender actuator 419 reduces an axial displacement of the benderactuator 419 in response to a given control signal magnitude.Conversely, decreasing the clamping force results in a greater axialdisplacement. In the embodiment of FIG. 2A, the load ring applies aclamping force around the whole peripheral edge 436 of the benderactuator 419. As will be appreciated, in an alternative embodiment, thebearing surface of the upper clamp ring 440 may be notched or cut out atdifferent locations around its circumference. Thus, no clamping force isdirectly applied to the portions of the peripheral edge 436 of thebender actuator 419 that are directly opposite the cutouts in thebearing surface of the upper clamp ring 440. It will be appreciated bythose of ordinary skill in the art that other clamping configurationsare possible as well, as described in detail above, without departingfrom the spirit and scope of the present invention.

The hydraulic pilot valve 420 is comprised of a movable valve 444, suchas a poppet for example, that is disposed in a cavity 445 in the housing432. The pilot valve 420 of FIGS. 2A and 2B is a three-way two-positionvalve. As will be appreciated, other comparable functioning valves maybe used in place of the poppet 444. The injector housing 432 has aninlet port 446 fluidly coupled with the supply line 447 of the hydraulicfluid source 422. Pressurized hydraulic fluid from the fluid source 422passes through a supply passage 448 that intersects cavity 445 of thehousing 432. Hydraulic fluid is returned to the fluid source 422 viadrain passages 450 that also intersect the cavity 445. Operation of thepilot valve 420 connects either the supply passage 448 or the drainpassage 450 to a control passage 452. As will be appreciated, thetwo-dimensional depiction of the passages 448, 450, 452 in FIG. 2A areschematic in nature. Often the pilot valve 420 is manufactured such thatthe passages 448, 450, 452 intersect the cavity 445 at differentcircumferential locations of the cavity 445.

In FIGS. 13A and 13B, the bender actuator 419 is illustrated in itsdomed, quiescent, unactuated state or position. When in the unactuatedstate, a center portion of the bender actuator 419 is displacedvertically upward to a flexed or domed position. An actuating pin orportion 454 of the poppet valve 444 is mechanically biased against alower side of the center portion of the bender actuator 419 by a biasingelement, such as a return spring 456 for example.

The actuating pin 454 is normally made from an electricallynonconducting material, such as zirconia for example. As will beappreciated, the actuating pin may be fabricated of other electricallyinsulating materials known to those who are skilled in the art.Alternatively, the end of the actuating pin 454 that is in contact withthe bender actuator 419 may be constructed to have an electricallynonconductive tip.

In the position illustrated in FIGS. 13A and 13B, the poppet valve 444has a first annular sealing area 458 that is separated from an annularlower seat 460 on the housing 432. Therefore, pressurized hydraulicfluid is free to flow from the supply passage 448 to the control passage452. Further, the poppet 444 has a second annular sealing area 462 thatis engaged with an annular upper seat 464, thereby blocking the flow ofhydraulic fluid from the control passage 452 to the drain passage 450.

With the poppet 444 in the position illustrated in FIGS. 13A and 13B,the pressurized hydraulic fluid is provided to a bottom 466 of the mainvalve 421, such as a spool valve for example. The supply passage 448also intersects an external annular passage or annulus 471 on the spoolvalve 421. Holes 473 provide a fluid connection between the annulus 471and a fluid cavity 470. Thus, the supply passage 448 providespressurized fluid to the cavity 470 that is contiguous with an upper endor top 472 of the spool valve 421. The spool valve is designed such thatwhen the pressurized hydraulic fluid is applied to ends, the forcesapplied by the pressurized hydraulic fluid are equal and opposite. Withequal fluid forces, the spool valve 421 is biased toward a closedposition illustrated in FIG. 13A by a biasing element 474, such as areturn spring for example.

With the spool valve 421 closed, the fluid passage 476 is fluidlyconnected to an annular fluid path or annulus 475 that in turnintersects a drain line 477. Thus, any fluid pressure in the fluid path476 is relieved when the spool valve 421 is in its upper, closedposition. Further, with the spool valve 421 in its closed position,hydraulic fluid in the supply passage 448 is blocked from entering thetop of the hydraulic fluid passage 476 that is connected to a cavity 498containing an intensifier piston 480. With no hydraulic fluid forcebeing applied to the top of the pressure intensifier 416, a biasingelement 482, such as a return spring for example, holds the intensifierpiston 480 at its uppermost position within the cavity 498.

With the poppet valve 420 in the position shown in FIGS. 13A and 13B,pressurized hydraulic fluid in control passage 452 is directed to acavity 484 above a check piston 486 connected to a nozzle check valve488. Pressurized hydraulic fluid above the check piston 486 forces thecheck piston 486 and nozzle valve 488 downward. An end 506 of the nozzlecheck valve 488 is sealingly engaged against an interior surface of thetip 490 of the fuel injector 412, thereby closing the nozzle check valve488 and prohibiting the flow of fuel from its output orifice 510.

The fuel injector 412 operates with a split injection cycle that has thefollowing five phases of injection: preinjection, pilot injection,injection delay, main injection and fill. The preinjection phase existswhen the engine is running and the injector 412 is between firingcycles. The preinjection phase is illustrated by the states of thevarious components of the fuel injector 412 illustrated in FIGS. 13A and13B. Hydraulic fluid pressure on the spool valve 421 is balanced; andtherefore, the spool valve 421 is held closed by the return spring 474,thereby stopping a flow of pressurized hydraulic fluid to theintensifier piston 480.

In its raised, closed position, the spool valve 421 separates from, andmechanically releases, spool pin 496 and ball check valve 492.Therefore, the pressure of any hydraulic fluid in fluid passage 476 isreleased around ball check valve 492 and out vent line 494. Thus, thepressure intensifier 416 is maintained inactive; and pressurizedhydraulic fluid in the control passage 452 holds the check piston 486and nozzle check valve 488 closed. Therefore, fuel received at the inletport 429 is not injected into a cylinder.

At the appropriate time, the ECM 430 initiates the pilot injection phaseby providing a first command signal to the bender actuator 419, such asa DC biasing voltage of a first polarity. Referring to FIGS. 14A and14B, the first command signal causes the bender actuator 419 to flex ina first direction, such as a generally vertically downward direction asviewed in FIG. 13A to a less domed or slightly domed, actuated, firstposition. It should be noted that with actuators currently available,such actuators never reach a flat state; and they will be destroyed byany flexure past center or a flat state.

The downward movement of the bender actuator 419 overcomes the biasingforce of the return spring 456 as the bender actuator 419 moves to itsactuated, first position. It should be noted that if the first commandsignal is removed, the bender actuator 419 will temporarily remain inthe position illustrated in FIGS. 14A and 14B until its chargesufficiently leaks off. Therefore, substantially less power is appliedto maintain the bender actuator 419 and other actuators, such as asolenoid for example.

Movement of the bender actuator 419 downward pushes the actuator pin 452and poppet 420 downward to a first position. With the poppet valve 420at its first position, the first annular sealing area 458 engages theannular lower seat 460, and the pressurized hydraulic fluid from thesupply passage 448 is blocked from the control passage 452. Further, thesecond annular sealing area 462 is separated from the annular upper seat464, thereby opening the control passage 452 to the drain passage 450.Thus, hydraulic pressure is removed from the bottom side 466 of thespool valve 421.

The pressure head in the cavity 470 at the top 472 of the spool valve421 overcomes the force exerted by the return spring 474, and the spoolvalve 421 moves vertically downward to an open position. As the spoolvalve 421 moves downward, it contacts the top of the spool pin 496; andthe spool valve 421 and spool pin 496 mechanically secure the ball checkvalve 492 in its seat area 497, thereby sealing the fluid passage 476from the vent line 494.

A displacement of the spool valve 421 to its lower, open positionterminates the fluid connection between the fluid path 476 and theannulus 475 and drain line 477. Further, displacement of the spool valve421 downward opens a fluid path via annulus 471 between the supplypassage 448 and the top of the fluid passage 476. Thus pressurizedhydraulic fluid from the cavity 470 is provided to fluid passage 476leading to the top of the intensifier piston 480 in the cavity 498. Theapplication of pressurized hydraulic fluid to the top of the intensifierpiston 480 forces the intensifier piston 480 downward in its cylinder orcavity 498. A plunger 500 operatively engages the intensifier piston 480to apply a very high pressure force on fuel within the cavity 502. Thepressure of the fuel entering the fuel injector 412 at inlet 429 may beabout 450 kPa or 65 psi. The intensifier piston 480 may increase thepressure of fuel within a nozzle cavity 504 to about 175 Mpa or 25,000psi as a function of the rail pressure. An inlet fill check valve 507prevents the high pressure fuel from flowing back out of the inlet port429. Of course, other fuel pressures are possible as well withoutdeparting from the spirit and scope of the present invention.

Opening the control passage 452 to the drain passage 450 also removesthe pressure of the hydraulic fluid over the check piston 486. As thepressure within the nozzle cavity 504 increases, a sufficient forcebuilds up on the end 506 of the nozzle check valve 488 to overcome theforce applied by the check piston return spring 508. The highlypressurized fuel in the nozzle cavity 504 effectively pushes the nozzlecheck valve 488 and the check piston 486 against the spring 508. The end506 of the nozzle check valve 488 is separated from its seat in the tip490, and highly pressurized fuel freely flows through the orifice ororifices 510 into the cylinder. The pilot injection phase continues aslong as the bender actuator 419 remains actuated; the spool valve 421remains open; and there is no pressurized hydraulic fluid on top of thecheck piston 486.

Subsequently, during the engine operation, an injection delay phase isinitiated by the ECM 430 providing to the bender actuator 419 a secondcommand signal such as a DC biasing voltage of an opposite polarity fromthe first command signal. The second command signal causes the benderactuator 419 to move in a second direction opposite the first direction,such as a generally vertically upward direction. The bender actuator 419moves to a more domed, quiescent pre-stressed, second position as shownin FIGS. 15A and 15B. As the bender actuator 419 moves upward, thereturn spring 456 moves the poppet 420 and actuating pin 454 upward to asecond position, such that the actuating pin 454 contacts the centerportion of the bender actuator 419.

Motion of the poppet 420 upward causes the second sealing area 462 toengage the upper seat 464, thereby disconnecting the control passage 452from the drain passage 450. Simultaneously, the first annular sealingarea 458 separates from the lower seal 460; and pressurized hydraulicfluid flows from the supply passage 448 to the control passage 452. Thereapplication of pressurized hydraulic fluid to the control passage 452creates a hydraulic force on top of the check piston 486. The checkpiston 486 and nozzle check valve are moved downward until the end 506engages the tip 490, thereby closing the nozzle check valve 488. Withthe nozzle check valve closed, the flow of fuel from the output orifice510 of the fuel injector 412 is terminated. Thus, injection of fuel intothe cylinder is terminated immediately after deactuating the benderactuator 419.

The application of pressurized hydraulic fluid to the control passage452 again applies a hydraulic fluid force to the bottom 466 of the spool421. That force in combination with a relatively weak force of thereturn spring 456 is slow to overcome the force of the pressurizedhydraulic fluid on the upper end 472 of the spool valve 421. Thus, thespool valve 421 is slow to move upward relative to the speed of closingof the nozzle check valve 488. During this period of initial slowoperation of the spool valve 421, pressurized hydraulic fluid continuesto flow past the spool valve 421 to the intensifier piston 480. With thenozzle check valve 488 closed and the continued application of ahydraulic force to the intensifier piston 480 and the plunger 500, thepiston 480 and plunger 500 continue to move downward. The continuedmovement of the intensifier piston 480 and plunger 500 again brings thefuel in the cavities 502 and 504 to the desired injection pressure inanticipation of the main injection phase. The duration of the injectiondelay phase is sufficiently small that the spool valve 421 never shutsoff the supply of pressurized hydraulic fluid to the top of theintensifier piston 480.

Subsequently, during the engine operation, the main injection phase isinitiated by the ECM 430 providing a third command signal to actuate thebender actuator 419. The third command signal is similar to the firstcommand signal that is described with respect to the pilot injectionphase. The third command signal is effective to cause the benderactuator 419 to move downward to its actuated, less domed, firstposition as illustrated in FIG. 16. The poppet valve 420 again changesstate and returns to its first position, thereby opening the controlpassage 452 to the drain passage 450. Pressure is immediately removedfrom the check piston 486, and the fuel in the cavity 504 that waspressurized during the delay cycle is effective to quickly open thenozzle check valve 488.

Simultaneously, removal of hydraulic pressure from the bottom 466 of thespool valve 421 quickly opens the partially closed spool valve 421,thereby applying full hydraulic fluid pressure to the top of theintensifier piston 480. The intensifier piston 480 and plunger 500continue their downward movement to maintain the desired injectionpressure on the fuel in the cavities 502, 504. The main injection phasecontinues for as long as the bender actuator 419 remains in its actuatedstate.

The main injection phase ends and the fill phase begins when the ECM 430provides a fourth command signal to the bender actuator 419. The fourthcommand signal is similar to the second command signal and causes thebender actuator 419 to move in the second, upward direction to itssecond, more domed, quiescent pre-stressed position as shown in FIG.13A. Again, in a manner similar to that described with respect to thedelay phase, the poppet valve 420 moves upward to its second position,thereby again applying pressurized hydraulic fluid to the controlpassage 452 and the top of the check piston 486.

The check piston 486 moves downward, thereby immediately closing thenozzle check valve 488 and terminating the flow of pressurized fuelthrough the orifice 510 of the fuel injector 412.

The pressurized hydraulic fluid in the control passage 452 alsoreestablishes a hydraulic force balance at the ends of the spool valve421, thereby permitting the return spring 474 to return the spool valve421 to its closed position. Closing the spool valve 421 terminates theflow of pressurized hydraulic fluid from the supply passage 448 to thefluid passage 476. Also, the fluid passage 476 is opened to the annulus475, so that hydraulic fluid pressure in the passage 476 is relievedthrough the drain 477. Further, as the spool valve raises away from thespool pin 496, the ball check valve 492 is able to release the pressureof the hydraulic fluid in the passage 476 via the vent 494.

As the pressurized hydraulic fluid is removed from the top of theintensifier piston 480, the return spring 482 pushes hydraulic fluid outof the cavity above the intensifier piston 480. The reverse check valve507 for the fuel inlet is lifted to its valve seat as the plunger 500 israised. This allows fuel to flow into the plunger cavity 502. The fillcycle is complete when the plunger 500 and intensifier piston 480 are attheir uppermost positions and the plunger cavity 502 is filled with fuelas shown in FIGS. 13A and 13B. At the end of the fill cycle, all of thecomponents of the fuel injector 412 are in respective states that definethe preinjection phase; and the fuel injector is ready for the next fuelinjection cycle.

While the use of hydraulic fluid is described herein, those of ordinaryskill in the art will appreciate that other fluids may be used as well,such as engine oil, fuel, transmission fluid, power steering fluid, andengine coolant by way of example without departing from the spirit andscope of the present invention. Moreover, it will be understood that thecheck valve 488 may be caused to open and close several times during aninjection cycle so as to provide, for example, pilot, main and postinjections.

With reference now to FIGS. 17-19, gasoline port injector 600 a and 600b are shown in accordance with the principles of the present invention.Port injector 600 a includes a valve body 602 having an axial fluidpassage 604 extending through the valve body 602 that communicatesbetween an inlet 606 and a fluid chamber 608 formed in the injector tip610. An elongated needle valve 612 is mounted to extend axially throughthe valve body 602 and includes a valve tip 614 that normally seats in avalve seat 616 to close a fluid orifice 618 formed at the remote end ofthe injector tip 610. The needle valve 612 is mounted for reciprocalmovement within the valve body 602 for selectively opening and closingthe orifice 618 during an injection cycle.

In accordance with one embodiment of the present invention, as shown inFIG. 17, the needle valve 602 is rigidly connected to at least onepiezoelectric device 622, such as a pre-stressed electroactive benderactuator, which may be thermally, mechanically or otherwisepre-stressed, as described in detail above. The bender actuator 622 mayhave a cylindrical or disk configuration and may be coated with anelectrically insulating and/or otherwise protective material as is wellknown in the art.

Bender actuator 622 may comprise a plurality of benders actuators(configured in parallel or in series) that are individually stacked orbonded together into a single multi-layered element. While not shown,those of ordinary skill in the art will appreciate that multiple benderactuators 622 may be mounted in parallel within the valve body 602 toincrease the force applied by the bender actuators 622 to the needlevalve 612 in response to a control signal applied by the ECM (not shown)to the bender actuator 622 through electrical leads 624 (one shown).Alternatively, the bender actuators 622 may be mounted in series toincrease the stroke of the needle valve 612 upon axial displacement ofthe bender actuators 622 in response to the control signal. The benderactuator 622 is mounted within the valve body 602 by a clamping and loadring assembly, illustrated diagrammatically at 628, as described indetail above in connection with FIGS. 7A, 7B, 8 and 11.

As shown in FIG. 17, a cylindrical coupling member 628 extends through abore 630 formed through the center of the bender actuator 622 and isfixed to the actuator 622 through a pair of locking collars 632 thatcontact the major surfaces 634, 636 of the bender actuator 622 and maybe threaded, welded, glued or otherwise fastened to the coupling member628. One end of the coupling member 628 is operatively connected to theneedle valve 612 through a fastener (not shown) or any other suitablemeans of attachment. Coupling member 628 includes an axial fluid passage638 (FIG. 17) extending at least partially therethrough that is in fluidcommunication with fluid passages 640 extending through a wall of thecoupling member 628. The passages 638, 640 permit fuel to pass from oneside of the bender actuator 622 to the other side through the couplingmember 628. As shown in FIG. 17, the needle valve 612 is connected tothe bender actuator 622 through the coupling member 628 so that theneedle valve 612 will travel axially within the valve body 602 uponaxial displacement of the bender actuator 622 from the domed, orunactuated configuration shown in FIG. 17 to a flattened, or actuatedposition (not shown).

In operation of the gasoline port 600 a of FIG. 17, the spring rate ofthe bender actuator 622 is used to bias the needle valve 612 to a closedposition so that the valve tip 614 seats in the valve seat 616 to closethe orifice 618. Fuel is delivered to the fluid chamber 608 in theinjector tip 610 through the axial fluid passage 604 and the fluidpassages 638, 640 that extend through the coupling member 628. During aninjection cycle, the ECM (not shown) applies a control signal to thebender actuator 622 that causes the bender actuator 622 to deform ordisplace axially by flattening out. As the bender actuator 622 flattensout in response to the control signal, the needle valve 612, by virtueof its rigid connection to the bender actuator 622, lifts off of thevalve seat 616 to open the orifice 618 for an injection of fuel. Afterthe injection cycle is complete, the control signal is eitherdiscontinued, or the polarity of the control signal is reversed, tocause the bender actuator 622 to return to its domed configuration asshown in FIG. 17.

A gasoline port injector 600 b in accordance with an alternative secondembodiment of the present invention is shown in FIG. 18, where likenumerals represent like parts to the gasoline port injector 600 a ofFIG. 17. In this embodiment, the bender actuator 622 may have arectangular configuration as shown in FIG. 19, although otherconfigurations are possible as well. The bender actuator 622 includes apair of opposite minor sides 642 a and a pair of opposite major sides642 b. A hole 644 is provided in the center of bender actuator 622 topermit direct attachment of the needle valve 612 to the actuator 622through a suitable fastener (not shown) as described in detail above. Inthis embodiment, multiple fluid passages 646 communicate with the axialfluid passage 604 and are routed through the valve body 602 and aroundthe minor sides 642 a of the bender actuator 622. In this way, thecoupling member 628 for passing the fluid through the bender actuator622 may be eliminated.

Referring now to FIG. 20, a fluid metering valve 700 a in accordancewith one embodiment of the present invention is shown. Fluid meteringvalve 700 a includes a plunger or piston 702 that is directly connectedto a bender actuator 704 as described in detail above. Bender actuator704 is supported by a support, shown diagrammatically at 706, that maycomprise the clamping and load ring assembly described in detail abovein connection with FIGS. 7A, 7B, 8 and 11. Bender actuator 704 may havea cylindrical or disk configuration and include at least oneelectroactive layer (not shown) positioned between a pair of electrodes(not shown), although other configurations are possible as well withoutdeparting from the spirit and scope of the present invention. In ade-energized or static state, the bender actuator 704 is preferablypre-stressed to have a domed configuration as shown in FIG. 20.

When the electrodes (not shown) of the bender actuator 704 are energizedto place the bender actuator 704 in an actuated state, such as when avoltage or current control signal is applied by an actuator controlsystem (not shown), the bender actuator 704 displaces axially byflattening out from the domed configuration. In particular, the benderactuator 704 displaces axially, i.e., flattens out, in one directionwhen it is actuated in response to a control signal of one polarity. Ina de-energized state, or in response to a control signal of an oppositepolarity, the bender actuator 704 displaces axially, i.e., returns toits domed configuration, in an opposite direction or the bender actuator704 may dome higher than its static state depending on the relayedcontrol signal. The bender actuator 704 is therefore bi-directional inits operation as described in detail above.

A portion of the plunger 702 extends into a fluid reservoir chamber 708having a variable volume defined by a lower end 710 of the plunger 702and an outlet check valve 712. A fluid inlet passage 714 communicateswith the fluid reservoir chamber 708 through an inlet check valve 716.The position of the lower end 710 of the plunger 702, and thus thevolume of fluid in fluid reservoir chamber 708, may be accuratelycalibrated or controlled by varying the voltage or current applied tothe bender actuator 704. Additionally, the static position of the benderactuator 704, and thus the static volume of the fluid reservoir chamber708, may be adjusted by varying the pre-load applied to the benderactuator 704 through the clamping and load ring assembly, illustrateddiagrammatically at 706.

Bender actuator 704 may comprise a plurality of bender actuators(configured in parallel or in series) that are individually stacked orbonded together into a single multi-layered element. While not shown,those of ordinary skill in the art will appreciate that multiple benderactuators 704 may be mounted in parallel to increase the force appliedby the bender actuators 704 to the plunger 702 in response to a controlsignal applied by the actuator control system (not shown).Alternatively, the bender actuators 704 may be mounted in series toincrease the stroke of the plunger 702 upon axial displacement of thebender actuators 704 in response to the control signal.

In operation, the fluid reservoir chamber 708 is filled with fluidthrough the fluid inlet passage 714 and the inlet check valve 716.During a fluid metering cycle, the bender actuator 704 is actuated by acontrol signal that causes the bender actuator 704 to displace axially,i.e., flatten out. The extent of the axial displacement, and thereforethe metering stroke of the piston or plunger 702, is accuratelycontrolled through the control signal applied to the bender actuator704. The plunger 702 can be accurately stroked to any position withinrange of motion of the bender actuator 704 in response to the appliedcontrol signal. As the plunger 702 displaces axially, the increasedpressure on the outlet check valve 712 causes the outlet check valve 712to open, thereby permitting a volume of fluid to be metered through thefluid metering valve 700 a. After a volume of fluid has been metered,the control signal is either discontinued, or the polarity of thecontrol signal is reversed, to cause the bender actuator 704 to returnto its domed configuration as shown in FIG. 20.

Referring now to FIG. 21, a fluid metering valve 700 b is shown inaccordance with an alternative second embodiment of the presentinvention, where like numerals represent like parts to the fluidmetering valve 700 a of FIG. 20. In this embodiment, a plunger 718 isbiased into engagement with the bender actuator 704 through a biasingelement, such as return spring 720. It will be appreciated that biasingof the plunger 718 into engagement with the bender actuator 704 could beachieved through other mechanical or hydraulic means as well.

The plunger 718 engages the bender actuator 704 so that the plunger 718will travel axially within the fluid reservoir chamber 708 upon axialdisplacement of the bender actuator 704 from the domed, or unactuatedconfiguration shown in FIG. 21 to a flattened, or actuated position (notshown) during a fluid metering cycle. After a fluid metering cycle iscomplete, the control signal is either discontinued, or the polarity ofthe control signal is reversed, to cause the bender actuator 704 toreturn to its domed configuration as shown in FIG. 21. The return spring720 returns the plunger 702 to its static position and maintainsengagement of the plunger 702 with the bender actuator 704.

Referring now to FIG. 22, a fluid metering valve 700 c is shown inaccordance with an alternative third embodiment of the presentinvention, where like numerals represent like parts to the fluidmetering valve 700 a of FIG. 20. In this embodiment, the plunger 702 iseliminated so that the bender actuator 704 acts directly upon the fluidwithin fluid reservoir chamber 708 during a fluid metering cycle. Thefluid reservoir chamber 708 includes a sealed fluid chamber 722 that isformed beneath the bender actuator 704.

During a fluid metering cycle, the bender actuator 704 is actuated by acontrol signal that causes the bender actuator 704 to displace axially,i.e., flatten out, and thereby increase the fluid pressure within fluidchambers 708 and 722. The extent of the axial displacement of the benderactuator 704, and therefore the increase in fluid pressure within thechambers 708 and 722, is accurately controlled through the controlsignal applied to the bender actuator 704. The increased pressure on theoutlet check valve 712 causes the outlet check valve 712 to open,thereby permitting a volume of fluid to be metered through the fluidmetering valve 700 c. After a volume of fluid has been metered, thecontrol signal is either discontinued, or the polarity of the controlsignal is reversed, to cause the bender actuator 704 to return to itsdomed configuration as shown in FIG. 22.

Referring now to FIG. 23, a fluid metering valve 700 d is shown inaccordance with an alternative fourth embodiment of the presentinvention, where like numerals represent like parts to the fluidmetering valve 700 a of FIG. 20. In this embodiment, fluid meteringvalve 700 d includes an inlet fluid passage 724 and one or more outletfluid passages 726 (two shown) communicating with the inlet fluidpassage 724. A control valve 728 selectively seals the outlet fluidpassages 726 from the inlet fluid passage 724 when a closing head 730 ofthe control valve 728 engages a valve seat 732.

One end of the control valve 728 remote from the closing head 730 isdirectly connected to the bender actuator 704 in a manner as describedin detail above. Other mountings of the bender actuator 704 and thecontrol valve 728 are possible as well without departing from the spiritand scope of the present invention. The control valve 728 is mounted forreciprocal movement for selectively opening and closing a fluid passagebetween the inlet fluid passage 724 and the outlet fluid passages 726through bi-directional operation of the bender actuator 704.

In operation, a control signal of a predetermined magnitude is appliedto the bender actuator 704 for a predetermined duration of time to causethe bender actuator 704 to displace axially, i.e., flatten out. Theextent of the axial displacement of the closing head 730 from the valveseat 732 is accurately controlled through the control signal applied tothe bender actuator 704 from an actuator control system (not shown). Theactuator control system (not shown) may include a programmable timer tocontrol the duration of time the control valve 728 is held in the openposition. A fluid pressure sensor (not shown) may be associated with theinlet fluid passage 724 and coupled to the actuator control system (notshown) for monitoring the fluid pressure within the inlet fluid passage724. Alternatively, the bender actuator 704 may be used as a pressuresensor so that the bender actuator 704 has a voltage or current outputthat is generally proportional to the fluid pressure within the inletfluid passage 724.

The actuator control system (not shown) is programmed to open thecontrol valve 728 so that a predetermined volume of fluid is meteredthrough the outlet fluid passages 726. As those of ordinary skill in theart will appreciate, the metered volume of fluid is determined by thefluid pressure within the inlet fluid passage 724 and the duration timethe control valve 728 is opened by the bender actuator 704.

Referring now to FIG. 24, a relief or reducing valve 800 in accordancewith the principles of the present invention is shown. In thisembodiment, relief or reducing valve 800 includes an inlet fluid passage802 communicating with a pressurized fluid system 804, and one or moreoutlet fluid passages 806 (two shown). A control valve 808 selectivelyseals the outlet fluid passages 806 from the inlet fluid passage 802when a closing head 810 of the control valve 808 engages a valve seat812. The closing head 810 of the relief or reducing valve 800 could bean angled seat type, flat seat type, needle valve type, spool valvetype, poppet valve type, or other valve type known to those of skill inthe art.

One end of the control valve 808 remote from the closing head 810 isdirectly connected to a bender actuator 814 in a manner as described indetail above. Other mountings of the bender actuator 814 and controlvalve 808 are possible as well without departing from the spirit andscope of the present invention. The control valve 808 is mounted forreciprocal movement for selectively opening and closing a fluid passagebetween the inlet fluid passage 802 and the outlet fluid passages 806through bi-directional operation of the bender actuator 814. As will bedescribed in detail below, in one embodiment where the control valve 808is a relief valve, the control valve 808 is selectively opened to avoidpressure extremes in the pressurized system 804. Alternatively, in oneembodiment where the control valve 808 is a reducing valve, the controlvalve 808 is selectively opened to provide a reduced fluid pressure inthe outlet fluid passages 806, such as for use in brake systems,differential locks, power-take-off clutches and other systems requiringa controlled fluid pressure within the system.

In operation, the bender actuator 814 may be used as a pressure sensorso that the bender actuator 814 has a voltage or current output that isgenerally proportional to the fluid pressure within the inlet fluidpassage 802 and the pressurized system 804. Alternatively, a separatepressure sensor (not shown) could be used. An actuator control system(not shown) receives the pressure information from the bender actuator814 or a separate fluid pressure sensor (not shown) and opens thecontrol valve 808 through a control signal of predetermined magnitude sothat either extreme pressures in the pressurized system 804 are avoidedor, alternatively, the fluid pressure in the outlet fluid passages 806is reduced to a predetermined pressure. In one embodiment where thecontrol valve 808 is a relief valve, after the fluid pressure isrelieved, the control signal is either discontinued, or the polarity ofthe control signal is reversed, to cause the bender actuator 814 toreturn to its domed configuration as shown in FIG. 24 to seat theclosing head 810 on the valve seat 812. In one embodiment where thecontrol valve 808 is a reducing valve, the control signal is adjusted toopen or restrict the fluid passage between the inlet fluid passage 802and the outlet fluid passages 806 to maintain the desired fluid pressurein the outlet fluid passages 806.

Referring now to FIG. 25, a direct valve 900 in the form of apiezoelectric device, such as a bender actuator 902 as described indetail above, is provided to selectively open and close a fluid aperture904. The bender actuator 902 is supported in a support, showndiagrammatically at 906, that forms a fluid seal about the entireperiphery of the bender actuator 902. The bender actuator 902 and thefluid seal around the entire periphery of the actuator 902 form a fluidchamber 908 that communicates with the fluid aperture 904 and fluidpassages 910. Additional fluid apertures (not shown) may communicatewith the fluid chamber 908.

The bender actuator 902 may have a cylindrical or disk configuration andmay be coated with an electrically insulating and/or otherwiseprotective material as well known in the art.

In a de-energized or static state, the bender actuator 902 is preferablypre-stressed to have a domed configuration as shown in FIG. 25 so thatthe fluid aperture 904 is opened. When the electrodes (not shown) of thebender actuator 902 are energized to place the bender actuator 902 in anactuated state, such as when a voltage or current control signal isapplied by an actuator control system (not shown), the bender actuator902 displaces axially by flattening out from the domed configuration todirectly seal with the fluid aperture 904 to prevent the flow of fluidfrom the fluid chamber 908 to the fluid passages 910. Of course, theorientation and operation of the bender actuator 902 could be changed sothat the bender actuator 902 directly seals the fluid aperture 904 inits static, or unactuated state, and opens the fluid aperture 904 in itsactuated state.

With reference now to FIGS. 26-27, direct-injection gasoline injectors1000 a and 1000 b are shown in accordance with the principles of thepresent invention. Injector 1000 a includes a valve body 1002 having anaxial fluid passage 1004 and multiple fluid passages 1006 extendingthrough the valve body 1002 that communicate between an inlet 1008 and afluid chamber 1010 formed in the injector tip 1012. An outwardlyopening, elongated check valve 1014 is mounted to extend axially throughthe valve body 1012 and includes a closing head 1016 that normally seatsin a conically-shaped valve seat 1018 to close a fluid orifice 1020formed at the remote end of the injector tip 1012. The check valve 1014is biased to the closed position by a biasing element, such as by areturn spring 1022, that acts on an annular flange 1024 extendingradially outwardly from the check valve 1014. The annular flange 1024includes multiple apertures 1026 that permit fluid flow from the axialfluid passage 1004 to the fluid chamber 1010. While not shown, it willbe appreciated in an alternative embodiment that the fluid may bediverted around the annular flange 1024 through one or more fluidpassages formed in the valve body 1002 (not shown). The check valve 1014is mounted for reciprocal movement within the valve body 1002 forselectively opening and closing the orifice 1020 during an injectioncycle.

In the embodiment of FIG. 26, one end of the check valve 1014 remotefrom the closing head 1016 engages at least one bender actuator 1028,such as a pre-stressed electroactive bender actuator, which may bethermally, mechanically or otherwise pre-stressed, as described indetail above. The check valve 1014 engages the bender actuator 1028 sothat the check valve 1014 will travel axially within the valve body 1002upon axial displacement of the bender actuator 1028 from the domed, orunactuated configuration shown in FIG. 26 to a flattened, or actuatedposition (not shown).

The bender actuator 1028 may have a rectangular configuration as shownin FIG. 19, although other configurations are possible as well. Thebender actuator 1028 may be coated with an electrically insulatingand/or otherwise protective material as well known in the art. Benderactuator 1028 may comprise a plurality of bender actuators (configuredin parallel or in series) that are individually stacked or bondedtogether into a single multi-layered element. While not shown, those ofordinary skill in the art will appreciate that multiple bender actuators1028 may be mounted in parallel within the valve body 1002 to increasethe force applied by the bender actuators 1028 to the check valve 1014in response to a control signal applied by the ECM (not shown) throughelectrical leads 1030 (one shown). Alternatively, the bender actuators1028 may be mounted in series to increase the stroke of the check valve1014 upon axial displacement of the bender actuators 1028 in response tothe control signal. The bender actuator 1028 is mounted within the valvebody 1002 by a clamping and load ring assembly, illustrateddiagrammatically at 1032, as described in detail above in connectionwith FIGS. 7A, 7B, 8 and 11.

In operation of the direct-injection gasoline injector 1000 a of FIG.26, the return spring 1022 biases the outwardly opening check valve 1014to a closed position so that the closing head 1016 seats in theconically-shaped valve seat 1018 to close the orifice 1020. Fuel isdelivered to the chamber 1010 through the axial fluid passage 1004 andthe multiple apertures 1026 formed in the annular flange 1024. During aninjection cycle, the ECM (not shown) applies a control signal to thebender actuator 1028 that causes the bender actuator 1028 to deform ordisplace axially by flattening out. As the bender actuator 1028 flattensout in response to the control signal, the check valve 1014, by virtueof its engagement with the bender actuator 1028, is pushed off of theconically-shaped valve seat 1018 against the force of return spring 1022to open the orifice 1020 for an injection of fuel. After the injectioncycle is complete, the control signal is either discontinued, or thepolarity of the control signal is reversed, to cause the bender actuator1028 to return to its domed configuration as shown in FIG. 26. Thereturn spring 1022 assists in returning the check valve 1014 to itsclosed position so that the closing head 1016 engages theconically-shaped valve seat 1018 to seal the orifice 1020.

Referring now to FIG. 27, a direct-injection gasoline injector 1000 b inaccordance with an alternative second embodiment of the presentinvention is shown, where like numerals represent like parts to thegasoline injector 1000 a of FIG. 26. In this embodiment, the elongatedcheck valve 1014 is rigidly connected to the bender actuator 1028 in amanner as described in detail above so that the bi-directional operationof the bender actuator 1028 is used to move the check valve 1014 to bothits open and closed positions. The rigid connection of the check valve1014 to the bender actuator 1028 permits the return spring 1022 to beeliminated so that the bender actuator 1028 provides the necessary forceto return the check valve 1014 to its closed position. As described indetail above, the spring rate of the bender actuator 1028 may beadjusted by the clamping and load ring assembly 1032 to pre-load thecheck valve 1014 against the conically-shaped valve seat 1018.

INDUSTRIAL APPLICABILITY

The common rail fuel injectors 1000 a-1000 e of the present inventionhave many advantages over common rail fuel injectors of the prior art.In each of the embodiments of FIGS. 1-4, the bender actuator 122directly controls the opening and closing of the elongated needle valve110 and check valve 138. Therefore, the hydraulic control chambernormally associated with common rail fuel injectors is eliminated. Thisremoves a source of variability in the operation of the common rail fuelinjectors 100 a-1000 d, and results in more precise and accurate controlover fuel metering during an injection cycle. In the common rail fuelinjector 1000 e, the bender actuator 122 directly controls the openingand closing of the control valve 170 to selectively communicate thecontrol fluid chamber 156 to the drain 171. This results in a moreprecise and accurate control over fuel metering during an injectioncycle than provided by solenoid, piezoelectric stack ormagnetorestrictive rod actuated control valves found in common rail fuelinjectors of the prior art.

The improved electrohydraulic actuator 310 of the present invention usesa bender actuator 312 as a mechanical power source. The bender actuator312 is physically small, uses little power, has very fast response timesand has a proportionally controllable bi-directional operation. Thus,the electrohydraulic actuator 310 is relatively small, has greatflexibility, and is power efficient.

Further, the use of a bender actuator 312 in the electrohydraulicactuator 310 provides significant advantages over electromagneticsolenoids.

First, the small mass and low inertia of a bender actuator 312 providesit with extremely fast response times, such as approximately 150microseconds. The fast response time allows for a very fast switchingtime of the poppet 330 as well as the device 315. Thus, the very fastresponse time of the electrohydraulic actuator 310 permits theelectrohydraulic actuator 310 to be used in a wide range ofapplications.

The bender actuator 312 has a further advantage of having a capabilityof proportional bi-directional operation. Thus, the poppet 330 can bemoved in both directions by means of different such as positive andnegative command signals. This allows for either the elimination of areturn spring 346 or the use of a substantially smaller return spring346. In addition, the capability of proportional bi-directional controlprovides an electrohydraulic actuator 310 that has the capability ofadjusting the velocity of the poppet 330 and the valve 314 hydraulicallyconnected to the poppet 330.

The bender actuator 312 has a still further advantage in that it drawsconsiderably less power than an electromagnetic solenoid. Further, dueto its capacitive behavior, a bender actuator 312 draws no power duringa “hold-in” period where actuation is maintained for a relatively longperiod of time.

In addition, multiple bender actuators 312 may be easily combined in astacked, parallel manner to provide a force that is approximatelylinearly related to the number of actuators in the stack. In addition,the actuators may be combined in a serial manner to increase themagnitude of the stroke, that is, the displacement. Even in a stackedarrangement, actuators are relatively small and may take up less spacethan electromagnetic solenoids and piezoelectric stacks.

The fuel injector 412 of the present invention provides many advantagesover solenoid-controlled fuel injectors of the prior art. For example,it is often difficult to accurately control movement ofsolenoid-controlled fuel injector valves through control signals appliedto the solenoid, especially when intermediate positioning of thesolenoid-controlled valve is desired such as in operation of the poppetand spool valves, 420 and 421, respectively. Factors such as inductivedelays, eddy currents and variability in components (i.e., springpreloads, solenoid force characteristics and varying fluid flow forces)must all be considered and accounted for in a solenoid-controlled fuelinjector design. Further, the response time of solenoids limits theminimum possible dwell times between multiple injection events and makesthe fuel injector generally more susceptible to various sources ofvariability. Additionally, components of a solenoid generally increasethe overall mass and power requirements of a solenoid-controlled fuelinjector system.

The pre-stressed bender actuator 419 of the present invention eliminatesthe drawbacks of known solenoid-controlled valves by providing rapid,accurate, and repeatable controlled movement of the poppet and spoolvalves, 420 and 421, respectively, between their open, partially openand closed positions. The bender actuator 419 of the present inventionis a generally lightweight, proportional device having a stroke outputthat is proportional to the input control signal. Accurate, repeatablebi-directional movement of the poppet and spool valves, 420 and 421,respectively, is controlled simply by varying the magnitude and polarityof the control signal applied to the bender actuator 419. Further, thebender actuator 419 of the present invention has a fast response time sothat dwell time between multiple injection events can be reduced,thereby also reducing variability from injection event to injectionevent. Additionally, pre-stressed bender actuator 419 acts as acapacitive load and will remain in its actuated position for a period oftime after the ECM control signal is terminated unlike a solenoid thatrequires a continuous voltage signal during its actuation phase.Therefore, the fuel injector 412 of the present invention is generallylighter and requires less power for operation than solenoid-controlledfuel injectors of the past.

Gasoline port injectors 600 a and 600b have the advantage that theneedle valve 612 used to open and close the fluid orifice 618 iscontrolled by the pre-stressed bender actuator 622 having all of theadvantages described in detail above in connection with bender actuators312 and 419.

In the fluid metering valves 700 a and 700 b, the bender actuator 704provides very accurate and repeatable bi-directional movement of theplungers 702 and 718 in the fluid reservoir chambers 708 to provideprecise metering of fluid from the outlet check valves 712.

In the fluid metering valve 700 c, the axial movement of the benderactuator 704 is accurately controlled to increase the fluid pressure inthe fluid reservoir chamber 708 and sealed fluid chamber 722. Theincrease in fluid pressure is accurately controlled to meter a volume offluid through the outlet check valve 712.

In the fluid metering valve 700 d, the bender actuator 704 is used tocontrol the position of control valve 728 relative to the valve seat732. The programmable timer coupled to the actuator control systemcontrols the duration of time the control valve 728 is opened, while thefluid pressure sensor associated with the inlet fluid passage 724 andcoupled to the actuator control system monitors the fluid pressurewithin the inlet fluid passage 724. The volume of fluid metered by themetering valve 700 d is determined by the fluid pressure within theinlet fluid passage 724 and the duration of time the control valve 728is opened by the bender actuator 704.

In the relief or reducing valve 800, the bender actuator 814 is used tocontrol the position of control valve 808. Control valve 808 controlscommunication of the inlet fluid passage 802 and the outlet fluidpassages 806. In one embodiment, where the control valve 808 is a reliefvalve, the control valve 808 is selectively opened to avoid pressureextremes in the pressurized system 804. Alternatively, in one embodimentwhere the control valve 808 is a reducing valve, the control valve 808is selectively opened to provide a reduced fluid pressure in the outletfluid passages 806.

In the direct valve 900, the bender actuator 902 is use to selectivelyopen and close fluid aperture 904. In a de-energized or static state,the bender actuator 902 is preferably pre-stressed to have a domedconfiguration as shown in FIG. 25 so that the fluid aperture 904 isopened. When the electrodes (not shown) of the bender actuator 902 areenergized to place the bender actuator 902 in an actuated state, such aswhen a voltage or current control signal is applied by an actuatorcontrol system (not shown), the bender actuator 902 displaces axially byflattening out from the domed configuration to directly seal with thefluid aperture 904 to prevent the flow of fluid from the fluid chamber908 to the fluid passages 910.

Direct-injection gasoline injectors 1000 a and 10000 b have theadvantage that the check valve 612 used to open and close the fluidorifice 1020 is controlled by the pre-stressed bender actuator 1028having all of the advantages described in detail above in connectionwith bender actuators 312 and 419.

While the present invention has been illustrated by a description ofvarious embodiments, and while these embodiments have been described inconsiderable detail, it is not the intention of Applicants to restrictor in any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is, therefore,not limited to the specific details, representative apparatus andmethod, and illustrative example shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of applicants' general inventive concept.

What is claimed is:
 1. A valve system, comprising: a valve body; a fluidchamber disposed within said valve body and adapted to communicate witha fluid source for containing fluid therein; a fluid orificecommunicating with said fluid chamber; a valve member mounted withinsaid valve body and movable between a closed position for closing saidfluid orifice and an open position for opening said fluid orifice; and apre-stressed bender actuator operatively engaging said valve member andoperable to selectively move said valve member to at least one of saidclosed and open positions to close and open said fluid orifice, whereinsaid valve member is rigidly connected to said bender actuator so thatsaid bender actuator is operable to move said valve member to saidclosed and open positions.
 2. The valve system of claim 1 furthercomprising a biasing element operatively engaging said valve member andoperable to effectively bias said valve member to said closed positionfor closing said fluid orifice.
 3. The valve system of claim 2, whereinsaid valve member includes a radially outwardly directed flange, saidbiasing element operatively engaging said radially outwardly directedflange and operable to effectively bias said valve member to said closedposition for closing said fluid orifice.
 4. The valve system of claim 1,wherein said valve system comprises a common rail fuel injector.
 5. Thevalve system of claim 1, wherein said valve member comprises a needlevalve.
 6. A valve system, comprising: a valve body; a fluid chamberdisposed within said valve body and adapted to communicate with a fluidsource for containing fluid therein; a fluid orifice communicating withsaid fluid chamber, a control fluid chamber disposed within said valvebody and adapted to communicate with a fluid source for containing fluidtherein and selectively to a drain for draining fluid from said controlfluid chamber; a valve member mounted within said valve body and movablebetween a closed position for closing said fluid orifice and an openposition for opening said fluid orifice, said valve member movingbetween said closed and open positions in response to a difference influid pressure in said fluid chamber and said control fluid chamber; acontrol valve member mounted within said valve body and operable to movebetween a closed position for containing fluid within said control fluidchamber and an open position for draining fluid from said control fluidchamber; and a pre-stressed bender actuator operatively engaging saidcontrol valve member and operable to selectively move said control valvemember to at least one of said closed and open positions.
 7. The valvesystem of claim 6, wherein said control valve member is rigidlyconnected to said bender actuator so that said bender actuator isoperable to move said control valve member to said closed and openpositions.
 8. The valve system of claim 6, further comprising a biasingelement operatively engaging said control valve member and operable toeffectively bias said control valve member to said closed position forcontaining fluid within said control fluid chamber.
 9. The valve systemof claim 6, wherein said bender actuator has a domed configuration thateffectively moves said control valve member to said closed position in astatic state of said bender actuator for containing fluid within saidcontrol fluid chamber.
 10. The valve system of claim 9, wherein saidbender actuator is operable to displace axially in an actuated state ofsaid bender actuator to effectively move said control valve member tosaid open position for draining fluid from said control fluid chamber.11. The valve system of claim 6 further comprising a biasing elementoperatively engaging said valve member and operable to effectively biassaid valve member to said closed position for closing said fluidorifice.
 12. The valve system of claim 6, wherein said fluid chamber isadapted to communicate with a prized fluid source.
 13. The valve systemof claim 6, wherein said control fluid chamber is adapted to communicatewith a pressurized fluid source.
 14. The valve system of claim 6,wherein said valve system comprises a common rail fuel injector.
 15. Anapparatus comprising: a prestressed electroactive bender actuatoroperable to receive a command signal and operable to move between firstand second positions as a function of the command a valve coupled withthe prestressed electroactive bender actuator, the valve being operatedin response to the prestressed electroactive bender actuator movingbetween the first and second positions, wherein the valve ismechanically coupled with the prestressed electroactive bender actuatorand the valve is moved by the prestressed electroactive bender actuatormoving between the first and second positions.
 16. The apparatus ofclaim 15 wherein the prestressed electroactive bender actuator movesthrough a displacement in a first direction in response to a firstcommand signal, and the valve is moved in the first direction to an openposition, thereby providing a supply of pressurized fluid.
 17. Theapparatus of claim 16 wherein the prestressed electroactive benderactuator moves through a displacement in an opposite direction inresponse to a second command signal, and the valve is moved in theopposite direction to a closed position, thereby terminating the supplyof the pressurized fluid.
 18. A method of operating a device in responseto a command signal comprising: applying a first command signal to theprestressed electroactive bender actuator; moving the prestressedelectroactive bonder actuator through a displacement in a firstdirection as a function of the first command signal; switching theprestressed electroactive bender actuator between first and secondoperating states as a function of the first command signal; switching avalve between first and second operating states as a function of theprestressed electroactive bender actuator switching between the firstand the second operating states, the valve operating the device as afunction of the valve switching between the first and the secondoperating states and supplying a pressurized fluid from the valve as afunction of the prestressed electroactive bender actuator moving throughthe displacement in the first direction, the pressurized fluid operableto switch the device to a first state; applying a second command signalto the prestressed electroactive bender actuator, moving the prestressedelectroactive bender actuator through a displacement in a seconddirection as a function of the second command signal; and terminating asupply of the pressurized fluid from the valve as a function of theprestressed electroactive bender actuator moving through thedisplacement in the second direction, the termination of pressurizedfluid operable to cause the device to switch to a second state.
 19. Themethod of claims 18 further comprising moving the valve in the seconddirection in response to the prestressed electroactive bender actuatormoving in the second direction.